1. Field of the Invention
The present invention relates to a motor driving apparatus such as an apparatus for driving a spindle motor of a hard disc drive (HDD) unit where a counter-electromotive force of the spindle motor is used for performing a retracting operation upon a voice coil motor (VCM) of the HDD unit.
2. Description of the Related Art
In an HDD unit formed by a spindle motor and a voice coil motor, when a power supply voltage applied to a spindle motor driving apparatus drops, a counter-electromotive force generated in the spindle motor is used to perform a retracting operation upon the voice coil motor, thus recovering the original position thereof.
In a prior art motor driving apparatus for a spindle motor, in order to supply a current due to the counter-electromotive force generated in the spindle motor to a motor driving apparatus for a voice coil motor, a reverse current preventing Schottkey diode is indispensible, which will be explained later in detail (see FIG. 5 of JP-A-7-45826).
In the above-described prior art motor driving apparatus however, in a normal operation mode, the power supply voltage minus a forward voltage of the reverse current preventing Schottkey diode is applied to the motor driving apparatus. Therefore, if the power supply voltage is low, it is impossible to effectively apply power to the spindle motor.